Dressing on a cylinder or a transfer cylinder as well as printing units of a printing press

ABSTRACT

A blanket is located on an outer surface of a roller, such as printing unit roller. The blanket has an elastic and/or a compressive layer with a surface pressure that depends on the degree of the impression. The layer is selected so that a depending of the surface pressure on the impression has, at least in some areas, a slope of less than 700 (N/cm 2 )/mm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is the U.S. National Phase, under 35 U.S.C. 371,of PCT/DE03/1157, filed Apr. 9, 2003; published as WO 03/08774A2 and A3on Oct. 23, 2003 and claiming priority to DE 102 17 402.4 filed Apr. 18,2002, and to DE 102 37 205.5 filed Aug. 14, 2002, the disclosures ofwhich are expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention is directed to a dressing on a cylinder, or on atransfer cylinder, as well as printing units of a printing press withthe cylinder. At least one of the cylinders has a dressing having anelastic and/or compressible layer.

BACKGROUND OF THE INVENTION

A printing blanket is known from DE 691 07 317 T2, which consists ofseveral layers and, in an extreme case, has a total thickness of from0.55 to 3.65 mm. The modulus of elasticity of the several layers ofcellular rubber lies between 0.2 to 50 MPa, or between 0.1 to 25 MPa.Because of the special structure of the printing blanket, and because ofthe properties of the several layers, a printing blanket is obtainedwhich, when indented, does not tend towards lateral shifting orprotuberances.

DE 19 40 852 A1 discloses a printing blanket for offset printing, whichblanket has a total thickness of almost 1.9 mm. A modulus of shearing,in the form of tension at 0.25 mm deformation in case of a thickness ofthe printing blanket, is stated to be approximately 4.6, 1.9 or 8.23kg/cm². The goal, in this case, is to achieve a quick recovery after anindentation, as well as to achieve a narrow thickness tolerance.

CH 426 903 discloses an offset printing blanket in which customaryindentation depths of 0 to 0.1 mm exist. An increase of the indentationfrom 0.05 to 0.1 mm requires, or has, at a result, a change in thesurface pressure of approximately 20.6 N/cm². This means that, in thisrange of indentation depth and with surface pressures of up toapproximately 40 N/cm², there would be a linearized “springcharacteristic” with a rise of approximately 412 N/cm²/mm.

WO 01/399 74 A2 discloses printing units with two cylinders, which twocylinders work together in the placed-together position. A formecylinder has an opening, in the area of its surface, in the form of anaxially extending groove for use in fastening one end of one or ofseveral printing formes. A transfer cylinder, which acts together withthe forme cylinder in a contact zone, has an elastic rubber blanket inthe area of its surface.

For the transfer of ink and other fluids between two cylinders of aprinting press, recourse is regularly had to the material combination ofhard-soft, for example in an inking and/or dampening unit, as well as inthe practice of an offset printing method between printing groupcylinders. The surface pressure required for ink transfer between thetwo cylinders is achieved by making an indentation in a resilient, suchas, for example, an elastomeric layer, which may be a soft elastomericcover/dressing, rubber blanket, or metal printing blanket, sleeve, by acooperating cylinder with a surface which is incompressible and which isalso inelastic, to a large degree.

Essential criteria for the uniform transfer of the fluid between thecylinders are a contact pressure, which is preset within narrow margins,as well as the constancy of the contact pressure. If fluctuations occurin the spacing distance between the cooperating cylinders, for examplebecause of cylinder out-of-roundness or because of vibrations induced byinterferences with the roll-off of the cylinders, the contact force, orthe surface pressure, changes, and thus the transfer behavior of thefluid also changes. At locations with interrupted or with reducedcontact, for example at the location of the plate or rubber blankettensioning groove, the surface pressure, for example, changesperiodically. This periodic change in surface pressure results in avibration excitation of the printing cylinders. In the field of printingtechnology, this change in surface pressure is expressed by changes inthe ink intensity in the resulting printed image. If, for example, thecontact pressure has been permanently changed through exteriorconditions such as longer wave interference, the danger of too faint orof too color-intensive printed products exists until the time ofcorrection. These products are typically considered as waste products.If the contact pressure is dynamically changed because of vibrations,such as shorter wave interference, this change in contact pressure isexpressed by the formation of visible stripes in the printed product.

SUMMARY OF THE INVENTION

The object of the present invention is directed to producing a dressingfor, or on a cylinder, the arrangement of this cylinder in relation to asecond cylinder, as well as to printing units of a printing press.

In accordance with the invention, this object is attained by theprovision of a dressing on a surface on a cylinder having an elastic orcompressible layer with a surface pressure as a function of anindentation. One of the cylinders, in a printing unit of two cylinders,and which has the elastic or compressible layer is a transfer cylinder.A contact width between the transfer cylinder and its cooperatingcylinder is at least 10 mm and is at least 5% of the effective cylinderdiameter. The indentation caused on the transfer cylinder surface may beat least 0.18 mm. At least one of the cylinders may have a dressing endreceiving groove which has a width, with respect to the width of thecontact zone, that is at most 1 to 3.

The advantages to be gained by the present invention reside, inparticular, in that a reduced sensitivity to changes, or tofluctuations, in the contact pressure or surface pressure, is achieved,and that because of this, a high quality of the printed product can beachieved in a simpler manner and can be maintained. By the use ofspecial dressings, by an optimized layout of the cylinders, as well asby their arrangement, it is possible to reduce the effects of anycylinder movements on ink transfer. In a particularly advantageousembodiment, with cylinders having narrow places of interrupted, or ofreduced contact, the vibration excitation itself is moreover reduced.

By the embodiment of the dressing and/or by the arrangement of thecylinders in relation to each other, the transfer of the fluid betweenthe two is considerably less affected. The same applies, for example, tointerferences that are induced by changes in the process, such achanging speed, changing thickness of the material; of a web, bringingfurther cylinders into or out of contact to spacing deviations whichoccur as a result of inaccuracies in the course of making contact, suchas stops, finite stiffness, or manufacturing tolerances; as well as tochanges in the dressing thickness because of wear; i.e. longer wavevibrations and/or incomplete restoration after passing through the niplocation; shorter wave or longer wave vibrations.

This is achieved, in particular, in that the dressing is configured insuch a way, or the cylinder is produced with an appropriate dressing,that a dependence of the resulting surface pressure or contact pressure,in the course of a variation of the indentation, extends considerablyflatter than is customary. A spring characteristic, i.e. an increase independence of the surface or contact pressure from the indentation,advantageously lies, at least in an advantageous range, for theindentation in the print-on position of at the most 700 (N/cm²)/mm.

An advantageous range of a relative indentation of the dressing, in theoperating state or in the print-on position, lies between 5% and 10%,for example. However, ranges for setting the relative indentation, whichranges differ as a function of the two cylinders working together, canbe preferred for achieving optimal results in view of the requiredtransfer of the fluids, along with a simultaneously small effect offluctuations.

In an advantageous embodiment of the present invention, the surface orcontact pressure, in the print-on position, varies, at most, within arange of between 60 and 220 N/cm². Or for various sub-ranges for fluids,such as, for example, printing inks, having greatly differentrheological properties, and/or different printing methods, in particularin these ranges, or sub-ranges, the curve should meet the requirementsmade on the rise.

Up to the present, the width of the contact zone, which is being createdby the pressure of the cylinders against each other in the nip, has, asa rule, been kept as narrow as possible. A widened nip location resultsin a higher linear force, and therefore results in increased staticbending. However, this disadvantage is compensated for by the dressingin accordance with the present invention, or the cylinder arrangement.In an advantageous embodiment, a width of the nip location is, forexample, at least 10 mm, and in particular, is greater than or equal to12 mm. An advantageous surface or contact pressure can be achieved withthis nip width.

For the case where a vibration is induced by an interference, such as,for example, by an interruption, on one of the surfaces of the cylinderswhich work together directly, or via a web, it is possible, by theconstruction of the dressing and/or by the arrangement of the cylindersin relation to each other, to also reduce the excitation of thisvibration, or to reduce its amplitude. This applies, in particular, toan embodiment of the present invention wherein a width of the cylindersurface interruption, in the circumferential direction, has, at most, aratio of 1:3 with respect to the width of the nip, or the imprint strip,caused by the indentation.

In general, the dressing, or the cylinder layer, permits the use ofslimmer, or also longer print cylinders. These are cylinders in which alength of the cylinders is large in comparison with the diameter of thecylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention are represented in thedrawings and will be explained in greater detail in what follows.

Shown are in:

FIG. 1, a schematic representation of the line forces between twocylinders while using a conventional dressing, in

FIG. 2, a schematic representation of the line forces between twocylinders while using a dressing in accordance with the presentinvention, in

FIG. 3, the measured surface pressure in a variation of the indentation,in

FIG. 4, a first preferred embodiment of a printing unit in accordancewith the present invention, in

FIG. 5, a second preferred embodiment of a printing unit, in

FIG. 6, a third preferred embodiment of a printing unit, in

FIG. 7, a fourth preferred embodiment of a printing unit, and in

FIG. 8, a schematic representation of a dressing with a support layer inaccordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIGS. 1 and 2, a machine, for example a printingpress, has cylinders 01, 02, which roll off on each other and whichtogether form a nip location 03, such as, for example, a cylinder gap03. In the case of a printing press, these cylinder 01, 02 can becylinders of an inking unit, a varnishing unit, or can be cylinders 01,02 of a printing unit. In the preferred embodiment of the presentinvention, that is represented in FIG. 1, the cylinders 01, 02 representa forme cylinder 01 of an effective diameter D_(wPZ), and a transfercylinder 02 of an offset printing unit. One of the cylinders 01, 02, forexample the transfer cylinder 02, has a dressing 05 or a cover 05 with asoft elastomeric layer 06 of a thickness “t” that is on the surface of alargely incompressible, inelastic cylinder core 04 of a diameterD_(GZK). The total thickness “T” of the dressing 05 is composed of, forexample, the thickness “t” of the soft, elastomeric layer 06, as well asa thickness of a support layer 10, which support layer 10 is possiblyconnected with the layer 06 and which is substantially incompressibleand inelastic, which support layer 10 may be, for example, a metalplate, shown, by way of example, in FIG. 8. If the dressing 05 does nothave an additional support layer 10, the thickness “t” corresponds tothe total thickness “T”. The layer 06 can be built up as aninhomogeneous layer 06 of several layers, which together have therequired properties for the layer 06. Together, the core 04 and thedressing or cover 05, constitute an effective diameter Ds24 _(wGZ) ofthe transfer cylinder 02. The effective diameter D_(wGZ) of the transfercylinder 02 is determined at the point of contact of the transfercylinder 02 with the surface of the forme cylinder 01 which surface ofthe forme cylinder 01 is effective for the roll-off, and which possiblyincludes a dressing 08, for example a printing forme 08, applied to thesurface of a forme cylinder base body 07. The cylinder 01 with the hardsurface can also be embodied as a counter-pressure cylinder 01, which isworking together with the transfer cylinder 02. The specific embodimentof the layer 06, as is explained in what follows, is not tied to theembodiments of the cylinders 01, 02 as transfer and forme cylinders 01,02, or to an embodiment of the cylinder 01 with a printing form 08.

As a function of the spacing between the two cylinders 01, 02, i.e. as afunction of their axial spacing distance A, the largely incompressibleinelastic surface of the forme cylinder 01 “dips” or intrudes orpenetrates into the soft layer 06 of the dressing or cover 05 on thetransfer cylinder 04 and causes an indentation S in that soft orresilient layer 06, in comparison to the undisturbed course of the layer06. Because of the restoring forces, a fluctuating or a changingindentation S, as a rule, leads to a fluctuating or to a changingsurface or contact pressure P in the cylinder gap 03, and causes thepreviously discussed problems in the quality of the ink transfer, and,in the, end, causes problems in the quality of the printed product.

A profile of a surface or contact pressure P in the nip 03 between thetwo cylinders 01 and 02, using a conventional dressing, is schematicallyrepresented in FIG. 1. The surface pressure P extends over the entirearea of the contact zone wherein, at rest, at a height of a connectingplane V between the axes of rotation of the two cylinders, the surfaceor contact pressure P reaches a maximum surface pressure P_(max). Duringproduction, the location of the area of maximum pressure shifts towardthe incoming gap side as a result of the viscous force portion. In aprojection onto a plane E, which plane E extends perpendicularly withrespect to the connection plane V, the contact zone, and therefore theprofile, has a width B. The maximum surface pressure P_(max) isultimately responsible for the ink distribution, and must be setaccordingly.

In comparison with FIG. 1, FIG. 2 schematically shows the profile of thesurface or contact pressure P in the case, in accordance with thepresent invention, of a greater indentation S, which simultaneouslycauses a widening of the width B. If it is now intended to achieve themaximum surface or contact pressure P_(max) in spite of this increasedwidth of the contact zone is, the integration of the surface or contactpressure P over the entire width B leads to an increase of a forcebetween the two cylinders 01, 02.

The absolute size of the surface pressure P in the cylinder gap 03, aswell as its fluctuation when the indentation S varies, is substantiallydetermined by a spring characteristic of the layer 06 used, or of thedressing 05 in which the layer 06 is used. The spring characteristicrepresents the surface or contact pressure P as a function of theindentation S. Some spring characteristics of customary dressings 05,and in particular of printing blankets 05 with an appropriate layer 06,are represented, by way of example, in FIG. 3. The values have beendetermined in the laboratory at a quasi-static die test stand. Theyshould be transferred, in a suitable manner, to values determined inanother way.

It can be seen in FIG. 3, that a rise ΔP/ΔS of the spring characteristicdetermines the fluctuation in the surface pressure P during the changeof the indentation S, for example in the case of a vibration. With avariation ΔS of the indentation around a mean indentation value S, thesize of a fluctuation ΔP of the required maximum surface pressureP_(max) in the cylinder gap 03 around the mean surface pressure P isapproximately proportional to the rise ΔP/ΔS of the springcharacteristic at the location S. Thus, in connection with a dressing“a”, as depicted in FIG. 3, for example, a reduction of the indentationS from −0.16 mm to −0.14 mm acts on the surface pressure P in the formof a reduction by approximately 50 N/cm², and a reduction of theindentation S from −0.11 mm to −0.09 mm acts on the surface tension inthe form of a reduction by approximately 25 N/cm². A dressing “b” has alesser rise, as also depicted in FIG. 3.

Dressings 05, which either as a whole, or whose layers 06 as such, havesuch a large rise ΔP/ΔS, in particular in the range of the requiredmaximum surface pressure P_(max) in the relevant pressure range, arecalled “hard” in what follows, those with a small rise ΔP/ΔS are called“soft”.

The dressing 05, or the layer 06, in accordance with the presentinvention are embodied as a “soft” dressing 05 or as a “soft” layer 06.In contrast to a “hard” dressing 05, or to a “hard” layer 06, identicalrelative movements of the cylinders 01, 02, or of the change of thedistance A, therefore lead to a lesser change of the surface or contactpressure P in case of a soft dressing 05, and therefore lead to, orresult in a reduction of the fluctuations in the ink transfer. Thus, thesoft dressing 05 of the present invention results in lesser sensitivityof the printing process to vibrations and/or to deviations of spacingsfrom a nominal value. With fewer changes in the surface pressure Pbecause of relative movements of the cylinders 01, 02, with the use ofsoft dressings 05, or with dressings 05 with a soft layer 06, vibrationstrips in the printed product, for example, only become visible atlarger vibration amplitudes.

In an advantageous embodiment of the present invention, the surface, orcontact pressure varies, at most, within a range of between 60 and 220N/cm². In connection with fluids, for example with printing inks withgreatly different rheologic properties, different ranges within theabove mentioned range of the surface pressure can be preferable. Thus,the range of the surface pressure, in connection with wet offsetprinting; i.e. with printing using ink and dampening agent, variesbetween 60 and 120 N/cm², and in particular between 80 to 100 N/cm², forexample, while in case of dry offset printing, with no dampening agent,and with only the application of ink to the forme cylinder the range ofthe surface or contact pressure varies between 100 and 220 N/m², and inparticular between 120 to 180 N/cm², for example. In these ranges, inparticular, the rise should meet the requirements for a rise.

The print-relevant range for the surface or contact pressure P_(max)advantageously lies between 60 and 220 N/cm². For fluids, for examplewith printing inks with greatly differing rheologic properties,different ranges within the above mentioned range of the surfacepressure can be preferred. Thus, the range for wet offset printingvaries, for example, between 60 and 120 N/cm², and in particular from 80to 100 N/cm². This is represented in FIG. 3. In case of dry offsetprintings, the range varies, for example, between 100 and 220 N/cm², andin particular from 120 to 180 N/cm². Thus, in an advantageousembodiment, a soft dressing 05, ]or its soft layer 06, has, at least inthe range of 80 to 100 N/cm², a rise ΔP/ΔS of, for example, ΔP/ΔS<700(N/cm²)/mm, and in particular ΔP/ΔS<500 (N/cm²)/mm. In the respectiverange for the surface or contact pressure P, the rise ΔP/ΔS should besmaller, by at least a factor of two, than is customary currently fordressings 05 in offset printing.

As schematically indicated in FIG. 2, in an advantageous embodiment ofthe present invention, the layer 06 has a greater thickness “t”, or thedressing 05 has a greater total thickness “T”, than has been previouslycustomary. The thickness “t” of the layer 06, which is functional inrespect to elasticity or compressibility, is for example 3.0 to 6.3 mm,and in particular is from 3.7 to 5.7 mm thick. Added to this elasticlayer 06 is the thickness of one or several support layers 10, which aresubstantially incompressible and inelastic, and which are possiblyconnected with the layer 06, if desired, on the side of layer 06 facingthe core 07, which support layers 10 are connected with the layer 06 forthe purpose of providing stability of shape and/or dimensions. Thissupport layer 10, or these support layers 10, which is/are functionallyeffective for the shape stability, can also be arranged between the“soft” layers 06. For example, support layer 10 can be embodied as sheetmetal, in particular of high-grade steel, of a thickness ofapproximately 0.1 to 0.3 mm. If the support layer 10 is in the form of awoven material, it can be 0.1 to 0.6 mm thick, depending on theembodiment of the dressing 05. In the case of several soft layers 06,the thickness “t” of the soft layer 06 relates to a sum of the possiblyseveral “partial layers”, which are functionally responsible for theabove described characteristic of dependence of surfacepressure/indentation, and to elasticity or compressibility. In thatcase, a dressing 05 with a soft layer 06, together with a support layeror layers 10, has a total thickness T of 3.5 to 6.5 mm, and inparticular of 3.9 to 5.9 mm.

The “soft” dressing 05 or the “soft” layer 06 is preferably operated ata greater indentation S in comparison with customary or knownindentations S, as schematically represented in FIG. 2 as comparisonwith FIG. 1, i.e. the two cylinders 01, 02 are put closer together inrelation to their respectively effective, but undisturbed diametersD_(wGz), D_(wPZ). Because of this, an optimal maximum surface pressureP_(max) is achieved in spite of a reduced rise ΔP/ΔS. In an advantageousembodiment, the placement of the cylinders 01, 02 against each other isperformed in such a way that the indentation S is at least 0.18 mm, is,for example, between 0.18 to 0.60 mm, and in particular is from 0.25 to0.50 mm.

A relative indentation S*, i.e. the indentation S in relation to thethickness “t” of the layer 06, without taking into consideration theparticular embodiment of the cylinders 01, 02, lies, for example,between 5% and 10%, and in particular lies between 6% and 8%.

In an advantageous embodiment, a width B of the contact zone, in aprojection perpendicularly to a connecting plane V of their axes ofrotation, resulting from the indentation S of the layer 06, is at least5% of the undisturbed effective diameter D_(wGZ) of the cylinder 02 withthe layer 06.

As described above, the embodiment and/or the arrangement of the “soft”dressing 05 is particularly advantageous, if one of the two cooperatingcylinders 01, 02, or even if both of the cylinders have an interference09, 11 on their effective surface, which affects the rolling-off. Thisinterference 09, 11, in the form of an interruption 09, 11, can be anaxially extending joint of two ends of one or of several dressings 05,08. In particular, the interference 09, 11 can also be caused by anaxially extending groove 09, 11 for use in fastening of the ends of oneor of several dressings 05, 08. This groove 09, 11 has an opening towardthe cylinder surface, through which opening the ends have beenconducted. In its interior, the groove 09, 11 can have a device forclamping and/or tensioning of the dressing 05, 08, or the dressings 05,08.

In the course of cylinder 01 rolling over the groove 09, 11, or thegrooves 09, 11 of cylinder 02, vibrations are induced. If, viewed in thecircumferential direction, the width B09, B11 of the groove 09, 11 isgreater than the width B of the contact zone, a vibration, with anincreased amplitude, is induced during the passage of the groove 09, 11since, because of the above mentioned greater width B of the contactzone, a larger linear force acts between the two cylinders 01, 02. Yet,because of the greater linear force, the increase of the vibrationamplitudes is less than the reduction of the sensitivity to vibrationsbecause of the softness of the layer 06, so that an overall reduction ofthe sensitivity to vibrations results.

It is of particular advantage to select the width B09, B11 of thegrooves 09, 11 to be less than the width B of the contact zone. In thiscase, at least areas of the cooperatively acting surfaces are alwaysupported on each other in the contact zone. In addition, a reduction ofthe size and a flatter course, or a widening of the pulse, results forthe force of the beating excitation. Therefore, with narrow grooves 09,11, the use of softer dressings 05, or softer layers 06, leads to aweakening and to a chronological lengthening of the groove beat.

In the case of the transfer cylinder 02, the ends of a metal printingblanket can be arranged in the groove 11. In this case, the layer 06 hasbeen applied to a dimensionally stable support, for example to a thinsheet metal plate, whose beveled ends are arranged in the groove 11. Thegroove 11 can be configured to be extremely narrow, for example having awidth less than, or equal to 5 mm, and in particular having a width lessthan or equal to 3 mm. Also, in the case of the forme cylinder 01, thegroove 09 is structured, in an advantageous embodiment, with a width inthe circumferential direction of less than or equal to 5 mm, and inparticular with a width of less than or equal to 3 mm.

Conversely, because of the contact zone, or the imprint strip, which islarger in comparison with prior art contact zones, the permissible ratioB09:B, or B11:B is reduced. An embodiment is of particular advantage,wherein the width B09, B11 of the groove 09, 11, in the area of itsopening, or mouth, toward the surface of the core 04, or the base body07, has, at most, a ratio of 1:3 in the circumferential direction inrelation to the width B of the contact zone or the imprint strip formedby the indentation.

Preferably, the soft layer 06 has a reduced damping constant incomparison with customarily employed materials. In spite of higherloading and release speeds, occurring during roll-of because of thelarger indentation S, no increased flexing heat is generated. Also, thelayer 06 must be embodied in such a way that a sufficiently rapidrestoration, or spring-back, into the initial position, takes placefollowing the passage through the cylinder gap 03 so that, for example,the initial thickness is again present in the course of contact with aninking roller or with a further cylinder.

A printing unit 12, which is configured in an advantageous manner withthe layer 06 and which is embodied as a so-called double printing unit12, is represented in FIGS. 4 and 5. The transfer cylinder 02, which isassigned to the forme cylinder 01, and which form a first cylinder pair01, 02, cooperates with a counter-pressure cylinder 14, that is alsoembodied as a transfer cylinder 14, and which is also assigned to aforme cylinder 16, via a material 13 to be imprinted, for example via aweb 13. All four cylinders 01, 02, 14, 16 are each driven, mechanicallyindependent of each other, by different drive motors 17, as seen in. Ina modification, the forme and transfer cylinders 01, 02, 14, 16 arecoupled in pairs and each pair is driven by a paired drive motor 17,either at the forme cylinder 01, 16, at the transfer cylinder 02, 14, orparallel to the cylinders, all as seen in.

In a first preferred embodiment, the forme cylinders 01, 16 and thetransfer cylinders 02, 14 are embodied as cylinders 01, 02, 14, 16 ofdouble circumference, i.e. as cylinders each with a circumference ofsubstantially two upright printed pages, in particular two newspaperpages. The cylinders are configured with effective diameters D_(wGZ),D_(wPZ) between 260 to 400 mm, and in particular between 280 to 360 mm.On the surface of the core 04, each of the transfer cylinders 02, 14 hasat least one dressing 05 of a total thickness T of between 3.5 to 6.5mm, and in particular between 3.9 to 5.9 mm. The rise ΔP/ΔS of thespring characteristic, at least in the print-relevant range, asdiscussed above, lies below 700 (N/cm²)/mm, and in particular lies below500 (N/cm²)/mm. The forme and transfer cylinders 01, 02, 14, 16 havebeen placed against each other in pairs in such a way that the width Bof the contact zone between the forme and transfer cylinders 01, 02, 14,16, in the position in which they are placed against each other, is from14 to 25 mm, and in particular is from 17 to 21 mm. By the use of thisconfiguration, the sensitivity of the printed product to vibrations andto inexact placement of the cylinders against each other has beenminimized to a large extent. The individual drive mechanisms, in theform of drive motors 17, aid this by the mechanical uncoupling.

In a second preferred embodiment of the present invention, which is notspecifically represented, the forme cylinders 01, 16 and the transfercylinder 02, 14 are embodied as cylinders 01, 02, 14, 16 each of singlecircumference, i.e. as cylinders each with a circumference ofsubstantially one upright printed page, and in particular of onenewspaper page. These cylinders are structured with effective diametersD_(wGZ), D_(wPZ) of between 150 to 190 mm. On the surface of the core04, the transfer cylinder 02, 14 has at least one dressing 05 of a totalthickness T of from 3.5 to 6.5 mm, and in particular of from 3.9 to 5.9mm. The rise ΔP/ΔS of the spring characteristic, at least in theprint-relevant range, as discussed above, again lies below 700(N/cm²)/mm, and in particular lies below 500 (N/cm²)/mm. The forme andtransfer cylinders 01, 02, 14, 16 have been placed against each other inpairs in such a way that the width B of the contact zone between theforme and transfer cylinders 01, 02, 14, 16, in the position in whichthey are placed against each other, is from 10 to 18 mm, and inparticular is from 12 to 15 mm.

In a third preferred embodiment, which is also not depicted, the formecylinders 01, 16 are embodied as cylinders 01, 16 of singlecircumference with effective diameters D_(wPZ) of between 150 and 190mm, and the transfer cylinders 02, 14 are embodied as cylinders 02, 14of double circumference with effective diameters D^(wGZ) of between 260to 400 mm, and in particular of from 280 to 350 mm. The transfercylinders 02, 14 each have at least one dressing 05 of a total thicknessT of from 3.5 to 6.5 mm, and in particular from 3.9 to 5.9 mm, on thesurface of the core 04. The rise ΔP/ΔS of the spring characteristic, atleast in the print-relevant range, as discussed above, again lies below700 (N/cm²)/mm, and in particular lies below 500 (N/cm²)/mm. The formeand transfer cylinders 01, 02, 14, 16 have been placed against eachother in pairs in such a way that the width B of the contact zonebetween the forme and transfer cylinders 01, 02, 14, 16, in the positionin which they are placed against each other is, from 12 to 20 mm, and inparticular is from 15 to 19 mm.

In a third preferred embodiment, which is also not depicted, the formecylinders 01, 16 are embodied as cylinders 01, 16 of singlecircumference with effective diameters D_(wPZ) of between 150 and 190mm, and the transfer cylinders 02, 14 are embodied as cylinders 02, 14of double circumference with effective diameters D_(wGZ) of between 260to 400 mm, and in particular of from 280 to 350 mm. The transfercylinders 02, 14 each have at least one dressing 05 of a total thicknessT of from 3.5 to 6.5 mm, and in particular from 3.9 to 5.9 mm, on thesurface of the core 04. The rise ΔP/ΔS of the spring characteristic, atleast in the print-relevant range, as discussed above, again lies below700 (Ncm²)/mm, and in particular lies below 500 (Ncm²)/mm. The forme andtransfer cylinders 01, 02, 14, 16 have been placed against each other inpairs in such a way that the width B of the contact zone between theforme and transfer cylinders 01, 02, 14, 16, in the position in whichthey are placed against each other is, from 12 to 20 mm, and inparticular is from 15 to 19 mm.

A printing unit 19 in accordance with the present invention isrepresented in FIGS. 6 and 7, which is either a part of a largerprinting unit, for example a five cylinder, nine cylinder or tencylinder printing unit, or which can be operated as a three cylinderprinting unit 19. Here, the transfer cylinder 02 works together with acylinder 18, which does not convey printing ink, for example acounter-pressure cylinder 18, such as a satellite cylinder 18. Now the“soft” surface of the transfer cylinder 02 works together with the“hard” surface of the forme cylinder 01 on the one side, and with the“hard” surface of the satellite cylinder 18 on the other side. In anembodiment, shown in FIG. 6, where at least the transfer cylinder 02 andthe satellite cylinder 18 are driven independently of each other, theone, or several satellite cylinders 18 have their own drive motor 17,while the pair consisting of the forme and transfer cylinders 01, 02 aremechanically coupled and are driven by a common drive motor.Alternatively, the forme and transfer cylinders 01, 02 can bemechanically independent of each other, and each driven by its own drivemotor 17, as seen in FIG. 7.

In a first embodiment in FIGS. 6 and 7, the forme cylinder 01, thetransfer cylinder 02 and the satellite cylinder 18 are embodied ascylinders 01, 02, 18, each of double circumference, and each witheffective diameters D_(wGZ), D_(wPZ), D_(wSZ) of between 260 to 400 mm,and in particular of from 280 to 360 mm. On the surface of the core 04,the transfer cylinder 02 has at least one dressing 05 of a totalthickness T of 3.5 to 6.5 mm, and in particular of 3.9 to 5.9 mm. Therise ΔP/ΔS of the spring characteristic, at least in the print-relevantrange, as discussed above, lies below 700 (N/cm²)/mm, and in particularlies below 500 (N/cm²)/mm. The forme and transfer cylinders 01, 02, aswell as the transfer cylinder 02 and the satellite cylinder 18, havebeen placed against each other in pairs in such a way that the width Bof the contact zone in the position in which they are placed againsteach other is from 14 to 25 mm, and in particular is from 17 to 21 mm.

In a second embodiment in FIGS. 6 and 7, the forme cylinder 01, thetransfer cylinder 02 and the satellite cylinder 18 are embodied ascylinders 01, 02, 18 of single circumference, i.e. each with acircumference of substantially one upright printed page, in particularone newspaper page. They are structured with effective diametersD^(wGZ), D^(wPZ), D^(wSZ) of between 150 to 180 mm, and in particular ofbetween 130 to 170 mm. On the surface of the core 04, the transfercylinder 02 has at least one dressing 05 of a total thickness T of from3.5 to 6.5 mm, and in particular of from 3.9 to 5.9 mm. The rise ΔP/ΔSof the spring characteristic, at least in the print-relevant range, asdiscussed above, again lies below 700 (N/cm²)/mm, and in particular liesbelow 500 (N/cm²)/mm. The forme and transfer cylinders 01, 02, as wellas the transfer cylinder 02 and the satellite cylinder 18, have beenplaced against each other in pairs in such a way that the width B of thecontact zone, in the position in which they are placed against eachother, is from 10 to 18 mm, and in particular is from 12 to 15 mm.

The changes implicit because of the greater softness, such as thegreater indentation S, the changed roll-off behavior, the largerthickness t or T, and the line must be taken into consideration in thelayout of the printing press. For example, a printing press operatingwith softer and thicker dressings 05, or layers 06, therefore haschanged, and in particular has increased cylinder undercuts or roll-offblanket thickness, as well as changed gap dimensions when cylinders areplaced against or away from each other due to blanket thickness, orindentation. Also, greater cylinder shift paths are required for theprint-off position because of the larger indentation.

The above mentioned dressing 05, or the layer 06, is arranged, forexample, in a printing unit with one or with several long, but slimcylinders 01, 02, 14, 16.

Thus, the forme cylinder 01, 16 and the transfer cylinder 02, 14 eachhave, for example, in the area of their barrels, a length, whichcorresponds to four or more widths of a printed page, for example anewspaper page. This width may be, for example from 1,100 to 1,800 mm,and in particular may be from 1,500 to 1,700 mm. The diameter D_(wGZ),D_(wPZ) of at least the forme cylinder 01, 16 is, for example, from 145to 190 mm, and in particular is from 150 to 185 mm, which diameter, incircumference, corresponds substantially to a length of a newspaper pageand is thus a “single circumference”. The device of the presentinvention is also advantageous for other circumferences in which a ratiobetween circumference and length of the cylinder 01, 02, 14, 16, 18 isless than or equal to 0.16, and in particular is less than 0.12, or iseven less than or equal to 0.08.

In another embodiment of the printing unit, in accordance with thepresent invention the length of the barrels of the forme and transfercylinders 01, 02, 14, 16 is, for example, from 1,850 to 2,400 mm, and inparticular is from 1,900 to 2,300 mm, and is dimensioned, in the axialdirection, for receiving, for example, at least six side-by-sidearranged upright printed pages in broadsheet format. In a variation ofthe invention, the diameter of at least the forme cylinder 01, 06 lies,for example, between 260 and 340 mm, and in particular lies between 280to 300 mm, and in another variation for example lies between 290 to 380mm, and in particular is from 300 to 370 mm, which, in circumference,corresponds substantially to two lengths of a newspaper page and is thusa “double circumference”. A ratio of the diameter D_(wGZ), D_(wPZ) of atleast the forme cylinder 01, 16 to its length here lies from 0.11 to0.17, and in particular from 0.13 to 0.16.

While preferred embodiments of a dressing on a cylinder, or a transfercylinder, as well as printing units of a printing press, in accordancewith the present invention, have been set forth fully and completelyherein above, it will be apparent to one of skill in the art thatvarious changes in, for example the dressing material, the mechanismsused to secure the dressings to a cylinder, and the like could be madewithout departing from the true spirit and scope of the presentinvention, which is accordingly to be limited only by the followingclaims.

1. A printing blanket adapted to be placed on a surface of a cylinder ina printing press, said printing blanket comprising: an incompressible,inelastic support layer; an elastic, compressible upper layer secured tosaid incompressible, inelastic support layer, said elastic, compressiblelayer having a thickness of at least 3.0 mm, said elastic, compressiblelayer exhibiting a contact pressure in response to a deformation of saidelastic, compressible layer, a spring characteristic of said elastic,compressible layer, which is expressed as a ratio of a change in saidcontact pressure to a change in said deformation of said elasticcompressible layer, being less than 700 (N/cm²)/mm in a range of anoperating pressure for said contact pressure from 80 to 180 N/cm² and ina range of said deformation from 0.22 mm to 0.38 mm.
 2. The printingblanket of claim 1 wherein, in use of said printing blanket in wetoffset printing, a range for said operating pressure is from 80 to 100N/cm².
 3. The printing blanket of claim 1 wherein, in use of saidprinting blanket in dry offset printing, a range of said operatingpressure is from 120 to 180 N/cm².
 4. The printing blanket of claim 1further including means releasably securing said printing blanket on asurface of a cylinder.
 5. The printing blanket of claim 1 wherein saidprinting blanket has a thickness of at least 3.5 mm.
 6. The printingblanket of claim 1 wherein said printing blanket has a width, in anaxial direction of the cylinder, of six widths of a printed page innewspaper format.
 7. The printing blanket of claim 1 wherein saidelastic, compressible layer is adapted to contact a web of material tobe imprinted.
 8. The printing blanket of claim 1 wherein saidincompressible, inelastic support layer is a dimensionally-stable metalsupport layer.
 9. The printing blanket of claim 8 wherein said metalsupport layer is sheet metal.
 10. The printing blanket of claim 1wherein said printing blanket is adapted for use in a printing group ofa printing press which prints printed pages in newspaper format.